Newly regenerated tarantula left hind limb metatarsus and tarsus (August 31, 2012). The entire region that has been replaced was lost during the previous molt (June 29, 2012). Click to enlarge.

The larger Honduran curlyhair tarantula (Brachypelma albopilosum) lost its rear hind leg’s metatarsus and tarsus during its last molt. A quick review of a few of the books in my library indicated that spider limb regeneration is surprising well understood.

Leg regeneration typically does not occur if the amputation occurs after the first quarter of an intermolt period, however it will occur two molts later in juveniles.

Regenerated appendages are smaller than the original appendage due to the high degree of folding necessary for development within the confines of the section immediately prior to the section that was amputated. All regions – including claws, spines and sensory organs – are present in the correct proportions.

Total return of function may not occur. Newly regenerated legs will have the full complement of 30 muscles and all attachments will be correct, though the number of muscle fibers will be reduced. Newly regenerated legs may be held at an angle, and their movements typically do not coordinate well with those of the original legs (Foelix, 2011).

I’m looking forward to seeing if/how the tarantula uses this leg during this intermolt period and after the next molt.

More to come!

Note that the regenerated tarantula left hind limb remains somewhat smaller than its normal counterparts. It should be identical to the other legs after the next molt. Click to enlarge.

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